The term PHP (Online Mendelian Inheritance in Man (OMIM) #103580 for PHP type 1A (PHP1A), #603233 for PHP type 1B (PHP1B) and #612462 for PHP type 1C (PHP1C)) describes disorders that share common biochemical features of hypoparathyroidism (that is, hypocalcaemia and hyperphosphataemia) that are the result of resistance of target tissues to the biological actions of parathyroid hormone (PTH). Here, PTH is linked to hypoparathyroidism.